I got a P0141 code telling me there's a "problem" with my downstream O2 sensor, as seen in the picture below. After a cold start, the voltage was reading 0.000 (Which I'm guessing makes sense considering the sensor was at ambient temperature which was in the 50's yesterday). Drove it home from work and let the engine heat up and then looked at the voltage again and it was in the .450 range. Is this a normal range? It doesn't swap negative and positive like the upstream sensors, does it? And if everything is working correctly, what would throw this code?

Thanks Ranger Fam.

Attached Images

	IMG_1883.jpg (86.0 KB, 8 views)
	IMG_1887.jpg (84.8 KB, 7 views)

__________________
2003 XLT 2WD 4.0L V6 SOHC
K&N Intake

If the wiring and connection to the sensor are fine then I would replace the sensor. I would use a MC or Denso,etc

__________________
2004 Ext Cab, 4WD, 4.0, Auto, 154k. (4.0 engine is out of a 2009 Ranger w/96k) ( as of 7/1/2017)

2004 Ranger, Ext Cab, 2WD, 3.0, 5 speed , 4WABS, crank windows, no cruise, Edge 116k.(6/5,2014) (SOLD).
1999 Ford Ranger, Reg Cab, 2.5, 5 speed, 2WD, no AC, 150k (SOLD).

I'll probably end up replacing it, yeah. Might try clearing the fuel trim memory first and let it learn the trims again. I just fixed a vacuum leak problem (see my thread on PCV replacement lol) where it was running lean for a while before I could find time to fix it, so the LTFT's are somewhat biased towards running lean still. If it comes back, that gives me better confirmation that it is an issue with the sensor.

__________________
2003 XLT 2WD 4.0L V6 SOHC
K&N Intake

I fix everything on my truck but I admit I'm anal about it, especially since a Denso is only $25. That being said if you don't mind the CEL and you don't have/need to deal with inspections you'll be fine. It's just the heating element plus the downstream sensors have no part in engine managnent.

__________________
2004 Ext Cab, 4WD, 4.0, Auto, 154k. (4.0 engine is out of a 2009 Ranger w/96k) ( as of 7/1/2017)

2004 Ranger, Ext Cab, 2WD, 3.0, 5 speed , 4WABS, crank windows, no cruise, Edge 116k.(6/5,2014) (SOLD).
1999 Ford Ranger, Reg Cab, 2.5, 5 speed, 2WD, no AC, 150k (SOLD).

I'm the same way. Just the fact that the CEL is on bothers me. Wanted to make sure there wasn't a quick fix first. Thanks for the help.

__________________
2003 XLT 2WD 4.0L V6 SOHC
K&N Intake

Update: Been periodically checking the engine with a scanner and now it's triggering P0136, 02S12 low voltage. Im pretty sure the O2 sensor is fried somehow. Replacing it this weekend and gonna see if it likes that.

__________________
2003 XLT 2WD 4.0L V6 SOHC
K&N Intake